Various forms of support arrangements are used for mounting in particular a motor vehicle seat on a mounting surface such as the floor of a motor vehicle body. Such support arrangements include means for adjustment of the seat in the fore-and-aft direction thereof, to provide variations in leg room for passengers and extension of the legs on the part of the driver when actuating foot-operated controls. In one form of such a support arrangement, as disclosed in German laid-open application (DE-OS) No. 25 26 018, the arrangement comprises an outer rail of C-shaped configuration and an inner rail which is slidably mounted therein. The arrangement includes a locking device for locking the inner and outer rails relative to each other, including a retaining lever having a locking member thereon, which engages into an opening in the support arrangement to lock the rails together. The lever has a spring member urging it towards the locked position and is carried pivotably in a mounting member which is disposed in the interior of the inner rail. The locking openings for receiving the locking member on the lever are provided in the outer rail.
However, as the mounting member for carrying the lever is disposed in the interior of the inner rail, the lever has to be fitted into the interior of the rail through an opening provided for that purpose in the rail, and then mounted to the mounting member in the rail. The fact that the lever can only be assembled by being fitted into the inner rail through the above-mentioned opening means that assembly of the arrangement involves a considerable amount of time which in turn has an adverse effect on the costs of production of that arrangement. In addition, any repair to the locking assembly or any replacement of a component thereof becomes a complicated process by virtue of the lever and the mounting member therefor being disposed within the inner rail.